Remote control and keying system for radio transmitters



Nov. 27, 1934. E. A. GOODWIN 1,981,861

REMOTE CONTROL AND KEYING SYSTEM FOR RADIO TRANSMITTERS Filed June 13, 1935 Xrroaw s/s Patented Nov. 27, 1934 UNITED squares REMOTE CONTROL AND KEYING SYSTEM FOR RADIO TRANSMITTERS Edwin 'A. Goodwin, Oceariport, N. J. Application June,13, 1933, Serial No. 675,626

6 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 376 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to signalling systems and more particularly to remote control apparatus for such systems.

It is often necessary or desirable to operate transmitters in fixed stations at points remote from the transmitter itself. The means commonly employed for this purpose requires the use of separate control lines to the plate and filament sources of power supply, and in addition a line for keying purposes must be provided. Such an arrangement requires that the operator turn on the switch for controlling filament and plate power before keying the transmitter. After he has concluded his transmissions, it becomes necessary for the operator to perform another switching operation to out off the plate and filament power supply.

From the standpoint of economy and simplicity, it is more desirable to place the transmitter under control of the operator by remote means. It is, therefore, an important object of the present invention to provide remote control means for raclio transmission systems whereby the operator simply presses the key to cause the transmitter to become operative and after transmission, leaves the key in open or inoperative position, which is sufficient to cause the power supply at the transat the local station. Itis only-necessary that the transmitter be first adjusted for operation on a desired frequency band and that voltages are correct.

Referring to the-drawing, a local or control station is shown as at A, in operative electrical communication with a remotely located transmitter as at B. The circuit system of station Acqm: prises an electron discharge device, here shown,

as a three element tube 1, having grid, plate and filamentelectrodes. It is understood that there is no restriction as to the type oftube, "it being only necessary that the tube have suffi cient current carrying capacity to operate the relay or relays through the instrumentality of. which the transmitter is controlled. Inthe grid circuit of the tube a condenser 2 is interpolated,

here shown as variable, and a variable resistance 3 is also provided, with ground connection as at 4. That. said condenser and resistance have impor-- tant functions to perform, will more fully appear as the description proceeds. A battery, 5 is con-- nected through said resistance and functions as a grid bias for tube 1. A source of plate supply is shown at 6 and the filament supply source is shown at '7. A filament rheostat of variable type is provided as at 9. The conventional key is shown at 10. A source of potential as at 8 is provided forthe operation of relay 38, andthis operation will hereafter be more fully described.

At B a transmitter of conventional type is' shown; Preparatory to detailing the operation of the control system in accordance with the 1 present invention, the main features of the transmitter will be described briefly. A master oscillator tube is shown at 11, with its tuning condenser l2 and having its plate'c-utput feeding into inductance 13, and operatively coupled through capacity 14 to power amplifier tube 15,. having its output or plate circuit tuned by variable condenser 16 [and feeding through transformer 17, to antenna system 18. Radio frequency choke coils are shown at 19, 20, 21, and 22. Numerals 23 and 24 designate biasing resistors. By-pass condensers are shown at 25, 26 and 27. The numerals 28 and 29 designate rectifier tubes. The plate transformer for said tubes is shown at 31'). Numerals 31, 32 and 33 designate the fila-.

merit transformers for the various tubes of the transmitter, the voltage for the system being taken from a. c. supply source as at 34. A bleeder resistor is shown at 35, and condensers 36 and 37, function as filter capacities. A keying relay, is shown as at 38, having its contacts at 3939, and having a keying resistor as at 40. The relay to control the filament supply for tubes 11 and 15 isshown at 4l,'havingcontacts at, 4242'.

The rectifier plate supply relay is shown at 43,"

In explaining the operation, the features of local station A will first be described. Referring to tube 1, the grid is normally at a negative poten-. tial due to battery 5. When the key 10 is depressed the circuit is completed from the key to battery 8 through the parallel path comprising the grid to filament of the tube to the ground and through resistance 3 and battery 5 to ground; thence through the ground to relay 38 and back to the key. This circuit neutralizes the negative potential on the grid due to battery 5, and at the same time places a positive charge on the condenser 2, because it is across the battery 5 to ground circuit. In fact, the positive charge is placed on the side of condenser 2 connected to the grid, where it is desired. This causes the grid to have a positive potential equal to the difference between the battery voltages 8 and 5. This action also energizes the relay 38, causing contact 39 to contact with 39. In addition, anode-cathode current flows through tube 1, and the relay or relays in the plate circuit will be energized. Re- Venting to the action in the grid circuit, as before stated, the condenser 2 takes a charge when the key is depressed, but the key does not have to remain depressed since the condenser is charged immediately. The key is thus tapped once or twice, once being sumcient. The charge on condenser 2 then begins to dissipate itself through the resistance 3 and the potential of the grid gradually diminishes until it reaches its negative value as determined by the battery 5. When this condition is reached, the tube ceases to pass current. To be exact, of course, the interelectrode capacity between grid and filament of tube 1 has the effect of a condenser in parallel with condenser 2, but for the purposes of the present invention this small capacitance may be disregarded. By choosing a proper value for condenser 2 :and resistance 3, such that the charge on 2 is not dissipated to a value to cause the tube 1 to become inoperative (i. e. due to absence of anode-cathode current) before the key 10 is again depressed (within reasonable limits as determined by an operator and his usual habits of keying), the tube remains operative and the conditions required by the invention are satisfied. This is in fact true. Condenser 2 and resistance 3 are of such values that the charge on 2 is not dissipated completely and the key is depressed again and again at normal transmission speeds and each time a charge is placed on 2 anew. The tube 1 remains operative and anodecathode current continues to flow until the end of transmission is reached, at which time the key is not depressed and the charge on 2 becomes again dissipated, the grid becoming negative with the result that no anode-cathode current flows.

In order to follow the complete cycle of operation, first the operator depresses key 10, which actuates the key relay 38 and causes tube 1 to pass current in the plate circuit due to the fact that the grid of said tube becomes positive in accordance with the action previously explained. Immediately, due to the passage of anode-cathode current, the fields of relays 41, 43 and 45 become energized, but the relays 41 and 45 have their respective contacts closed, thus energizing the filament transformers 31, 32 and 33 to supply filament power to tubes 11, 15, 28 and 29. Relay 43 is of time delay type that allows the filaments to become supplied with power before its contacts close. is suflicient time for this action to take place, then relay 43 operates and energizes the plate Let it be assumed that two seconds voltage transformer 30 and supplies plate voltage to all of the transmitter and rectifier tubes. Returning to the operator, he depressed key 10 and then allowed it to spring back to its normal nondepressed position. He waited, say two seconds, for all relays to become operative (the values of condenser 2 and resistance 3 at station A being sufficient to cause anode-cathode current to remain flowing for several seconds in tube 1) and he then begins to transmit. The transmitter does not operate until relay 33 is energized again, it being de-energized when the operator allowed the contacts of key 10 to separate. The transmitter, however, is in operating condition as soon as relay 43 actuates its closing contacts 44 and 44. As each message character is tapped on the key 10, a new charge is placed on condenser 2, and tube 1 continues to pass current in the anode cathode circuit extending from battery 6 to the plate of tube 1, to the filament of said tube, to ground; thence through ground to relay 45, to relay 43, to relay 41 and back to battery 6. Also, as each impulse is transmitted, keying relay 38 is actuated, which causes the filament of tube 15 to be at ground potential and in eifect to key the transmitter. At the end of transmission, keying relay 38 becomes de-energized when the operator allows key 10 to assume its open condition, the charge on condenser 2 gradually becomes dissipated through resistor 3 until the grid of tube 1 becomes negative thus preventing the passage of anode-cathode current, which results in relays 41, 43 and 45 becoming de-energized, their respective contacts opening and the transmitter power being cut oif and again reverting to a non-operative state awaiting the next transmission.

I claim:

1. In a system of the character described, comprising a control station in electrical communication with a remotely located radio transmitter; power supply circuits for the transmitter; relay actuated means in said circuits, to place said transmitter in operative condition; a solenoidally actuated key circuit for the transmitter; an electron tube operative with the control station and means for normally blocking the said tube; a circuit connecting the relay actuated means with the anode-cathode path of said tube; a relay actuated switch for said transmitter and a circuit connecting the windings of the said relay with the grid-cathode path of said tube, and including a key functioning to control the fiow of energy through said tube and to transmit signalling impulses to said transmitter through said key circuit; means in the grid circuit of the tube comprising a positive source of potential to place said tube in conductive condition when said key is depressed; and means to maintain the tube in conductive condition comprising an electrical condenser charged by the action of said key and including a resistance to prevent the discharge of the condenser while normally transmitting signal impulses.

2. In a system of the character described, which includes a control station in electrical communication with a remotely located relay operated transmitter; a power supply circuit for the transmitter solenoidally actuated switches in said supply circuit; means for controlling the transmitter from said station comprising an electron tube normally biased to non-conductive condition; a circuit connecting the windings of said switches and the anode-cathode path of said tube; a solenoidally actuated switch for said transmitter, and a circuit connecting the windings of said switch with the grid-cathode path of the tube and including a control key operative through the tube to transmit signalling impulses; and means to maintain said tube in conductive condition in response to the action of said key and while norimpulses, said i mally transmitting signalling means including an electrical condenser charged by an initial movement of the key, a charging source of potential, and a resistance to regulate the rate of discharge of said condenser.

3. A system of controlling a remotely located transmitter, comprising a control station and including circuits operatively connecting said station and transmitter; power supply circuits for the transmitter; means comprising relays in said supply circuits and operative at difierent times to place said transmitter in condition to transmit signals; means at the said station comprising an electron tube normally biased to prevent passage of current from said station to said relays; a circuit connecting the windings of said relays and the output of said tube; a solenoidally actuated switch for said transmitter and a circuit connecting the windings of said switch with the input of said tube, and including a key functioning through said tube both to control said switch and to transmit signalling currents to said transmitter; means actuated by the key to cause said tube to become conductive for a predetermined time interval in order to initiate the operation of the transmitter; and means to maintain said conductive condition during normal operation of said key while transmitting signals.

4. In a system of the character described, comprising a control station in electrical communication with a remotely located transmitter; power supply circuits for the transmitter; means comprising relays in said supply circuits to initiate the operation of the transmitter; means at the control station comprising an electron tube normally biased to prevent passage of current energy to said relays; a circuit connecting the windings of said relays and the anode of said tube; a solenoidally actuated switch for said transmitter and a circuit connecting the windings of said switch with the grid of said tube, and including a key functioning both to control said switch and to transmit signalling impulses; means to cause said tube to become conductive for a predetermined time interval, said means comprising a condenser, and an energy source for charging the condenser and for placing a positive potential on the grid of said tube in response to an initial movement of said key; and means to maintain said conductive condition during normal transmission of signal impulses by said key, said means comprising a resistance operative with the condenser to retard its rate of discharge.

5. In a system of the character described, comprising a control station in electrical communication with a remotely located radio transmitter; power supply circuits for the transmitter; relay actuated switches in said supply circuits; an electron tube operative with the control station and means for normally blocking said tube; a circuit connecting the windings of said relays with the anode-cathode path of said tube; a relay actuated switch for said transmitter and a circuit connecting the windings of the relay with the gridcathode path of said tube, and includinga key functioning to control the flow of energy through said tube and to transmit signalling impulses to said transmitter; means actuated by said key to place the tube in conductive condition, comprising a condenser connected to the control grid of the tube and including a charging source of energy; and means to maintain said conductive condition during normal transmission of signal impulses, said means comprising a resistance element to control the rate of discharge of said condenser.

6. In a system of the character described, comprising a local station in remote electrical communication with a radio transmitter; power supply circuits for the transmitter; relay means included in said supply circuits for initiating the operation of the transmitter; and means at the local station for controlling both the relay means and signalling currents, comprising a key; an electron tube normally biased to non-conductive condition; a circuit connecting the relay means a condition during normal transmission of signalling current impulses by said key, including resistance means operative with the condenser to control its rate of discharge.

' EDWIN A. GOODWIN. 

